1. Field of the Invention
This invention relates to a data-transmission and data-processing system, and more particularly to an improved data-transmission and data-processing system which is capable of curtailing a time required for accessing, by data from a single central station, data receiving stations selected from a plurality of data receiving stations.
2. Description of the Prior Art
In a known pay-TV system, an address of every decoder to be accessed must be transmitted so that a broadcasting station may access decoders of receiver units, addressing respective decoders. It takes a considerable time to access a large number of decoders unless data transmission speed can be increased. Thus, this conventional system has been impracticable.
It is now assumed that there are N decoders which are all in the condition of "X" and that it is now desired to put decoders having addresses A.sub.n to A.sub.m into the condition of "Y" and put the remaining decoders into the condition "Z". In the case where the data to be transmitted by the broadcasting station includes both A (address) and condition indication, the format of the data is:
A.sub.O Z.multidot.A.sub.1 Z . . . A.sub.n-1 Z.multidot.A.sub.n Y.multidot.A.sub.n+1 Y . . . A.sub.m Y.multidot.A.sub.m+1 Z . . . A.sub.N Z
Therefore, if it takes a time t to transmit one item of data, a time required for transmitting all of the data will be Nt. Thus, as described above, the required time becomes longer as the number of items of data to be transmitted increases.